Agrobacterium radiobacter was isolated from 15 blood cultures collected from 15 newborns. Contamination of blood cultures was suspected because, in most cases, the babies' illnesses seemed incompatible with infection. A radiobacter was isolated from citrated tubes used for clotting-factor studies. Review of venipuncture technique revealed that occasionally the coagulation study tubes were being inoculated before the blood-culture bottles. This investigation demonstrated how an environmental source coupled with faulty technique caused a cluster of false-positive blood cultures.